Rotary kilns

ABSTRACT

A rotary kiln comprises an inclined kiln barrel mounted on a supporting framework by upper and lower bearing members at the ends of the kiln barrel. The supporting framework is fitted with longitudinal bed plates and the upper and lower bearing members for the kiln barrel have support brackets which are fitted with bearing pads sealing on the bed plates through intermediate support members which lie in longitudinal grooves in the bed plates below the bearing pads of the support brackets for the bearing members. In the case of the lower bearing member the intermediate support members are in the form of rods lying in the longitudinal grooves of the bed plates below the bearing pads of the support brackets which are rigidly bolted to the bed plates. In the case of the upper bearing member the intermediate support members take the form of ball bearings running in the longitudinal grooves of the bed plates below the bearing pads of the support brackets. Thus the upper bearing member is free to move longitudinally with respect to the bed plates to accommodate for longitudinal thermal expansion of the kiln barrel. An inlet hopper is similarly mounted on the bed plates at the upper end of the kiln barrel by a movable support bracket at its other end. The inlet hopper connects with the kiln barrel through a slidable sealing means to accommodate for relative thermal expansion between the inlet hopper and the kiln barrel.

United States Patent Gillies et al.

[ 1 ROTARY KILNS [72] Inventors: George Marshall Gillies, St. Annes;James Edgar Littlechild, Lytham, both of England [73] Assignee: UnitedKingdom Atomic Energy Authority, London, England [22] Filed: April 9,1971 [2]] Appl. No.: 32,649

[30] Foreign Application Priority Data April 23, 1970 Great Britain..l9,664/70 May 11, 1970 Great Britain ..22,749/70 [52] U.S. Cl...263/32 R [51] lnt. Cl ..F27b 7/20 [58] Field of Search ..263/33 R, 32R [56] References Cited UNITED STATES PATENTS 2,434,845 l/l948 Gaffney..263/32 X 3,396,953 8/1968 Sandbrook ..263/33 R Primary Examiner-JohnJ. Camby Attorney-Larson, Taylor & Hinds [57] ABSTRACT A rotary kilncomprises an inclined kiln barrel [451 Oct. 17, 1972 mounted on asupporting framework by upper and lower bearing members at the ends ofthe kiln barrel.

The supporting framework is fitted with longitudinal bed plates and theupper and lower bearing members for the kiln barrel have supportbrackets which are fitted with bearing pads sealing on the bed platesthrough intermediate support members which lie in longitudinal groovesin the bed plates below the bearing pads of the support brackets for thebearing members. In the case of the lower bearing member theintermediate support members are in the form of rods lying in thelongitudinal grooves of the bed plates below the bearing pads of thesupport brackets which are rigidly bolted to the bed plates. In the caseof the upper bearing member the intermediate support members take theform of ball bearings running in the iongitudinal grooves of the bedplates below the bearing pads of the support brackets. Thus the upperbearing member is free to move longitudinally with respect to the bedplates to accommodate for longitudinal thermal expansion of the kilnbarrel. An inlet hopper is similarly mounted on the bed plates at theupper end of the kiln barrel by a movable support bracket at its otherend. The inlet hopper connects with the kiln barrel through a slidablesealing means to accommodate for relative thermal expansion between theinlet hopper and the kiln barrel.

8 Claims, 11 Drawing Figures PATENTEDncr 17 1912 3,698,697 SHEET 02 0F11 PATENTED OCT 1 7 I972 SHEET OSUF 11 IIIIIIIIIIIIIIIII PATENTEDucI 11I972 PATENTED GET 1 7 I972 SHEET UBUF 11 PATENTED 3.698.697 SHEET USUF11 PATENTEDom 17 I972 SHEET lOUF 11 PATENTEDUBI 1 1 I972 3. 6 98 69 7SHEET 11 HF 11 ROTARY KILNS BACKGROUND OF THE INVENTION This inventionrelates to rotary kilns and in particular relates to an improved form ofrotary kiln for carrying out gas/solids reactions.

SUMMARY OF THE INVENTION According to the invention a rotary kilncomprises a cylindrical kiln barrel rotatably mounted on a supportingframework by a bearing member at each end of the kiln barrel, an inlethopper being mounted on the supporting framework at one end of the kilnbarrel, a discharge hopper being mounted on the supporting framework atthe other end of the kiln barrel, slidable sealing means connecting theinlet hopper with the ad jacent end of the kiln barrel, slidable sealingmeans connecting the discharge hopper with the other adjacent end of thekiln barrel, the inlet hopper being mounted on the supporting frameworkby supports adjacent to each end of the inlet hopper, the supports atone end of the inlet hopper being rigidly fixed to the supportingframework, the supports at the other end of the inlet hopper beingmovably mounted on the supporting framework so as to allow forlongitudinal thermal expansion of the inlet hopper relative to thesupporting framework on rise of the inlet hopper from ambient tooperating temperature, the bearing member at one end of the kiln barrelbeing mounted on the supporting framework by supports which are rigidlyfixed to the supporting framework, the bearing member at the other endof the kiln barrel being mounted on the supporting framework by supportswhich are movably mounted on the supporting framework so as to allow forlongitudinal thermal expansion of the kiln barrel relative to thesupporting framework on rise of the kiln barrel from ambient tooperating temperature, the discharge hopper being mounted at least atone point on the supporting framework by supports which are rigidlyfixed to the supporting framework, relative longitudinal movementsbetween the kiln barrel and the inlet and discharge hoppers due tothermal expansion being accommodated by the slidable sealing meansbetween the inlet and discharge hoppers and the ends of the kiln barrel.

The supporting framework may be fitted with bed plates, the supports forthe inlet hopper, the outlet hopper and the bearing members for the kilnbarrel comprising support brackets fitted with bearing pads seating onthe bed plates through intermediate support members. Where the supportsare to be movably mounted on the supporting framework, as in the case ofthe supports at the one end of the inlet hopper and the supports for thebearing member at one end of the kiln barrel, the intermediate supportmembers between the bed plates and the bearing pads on the supportbrackets may be in the form of rolling bearing members such as ballbearings lying in longitudinal grooves in the bed plates, the bearingpads having corresponding longitudinal grooves in their underfacesseating on the ball bearings. In the case where the supports arerigidlyfixed to the supporting framework, the intermediate supportmembers between the bed plates and the bearing pads may be in the formof rods lying in the longitudinal grooves in the bed plates, the bearingpads having corresponding longitudinal grooves in their underfacesseating on the rods and means being provided for clamping the supportbrackets rigidly to the bed plates with the intermediate rods clampedbetween the bed plates and the bearing pads on the support brackets.

Also according to the invention one form of slidable sealing means forconnecting either the inlet or the discharge hopper with the adjacentend of the kiln barrel comprises a cylindrical member mounted coaxiallyfrom the end of the kiln barrel and extending longitudinally into theannular interspace between inner and outer coaxial sleeves mountedaround an aperture in the wall of the related hopper, alip seal assemblybeing located in the annular interspace between the outer sleeve and thecylindrical member and sealing with the outer surface of the cylindricalmember, a second lip seal assembly being located closing the annularinterspace between the cylindrical member and the inner sleeve at theend of the cylindrical member remote from the kiln barrel. In the abovearrangement a helical scroll member may be fitted in the annularinterspace between the cylindrical member and the inner sleeve on theside of the second lip seal assembly open to the kiln barrel, the scrollmember being mounted on the inner surface of the cylindrical member sothat rotation of the cylindrical member with rotation of the kiln barrelresults in the removal of any powdered material which infiltrates intothe annular interspace between the cylindrical member and the innersleeve.

A scroll assembly may be fitted in the base of the inlet hopper to moveany powdered material which deposits in the base of the inlet hopperinto the kiln barrel, said scroll assembly being mounted from one end atthe end of the inlet hopper remote from the kiln barrel by a bearing andseal assembly, the other end of the scroll assembly being coupled withthe end of the kiln barrel so that the scroll assembly is rotated withrotation of the kiln barrel.

DESCRIPTION OF THE DRAWINGS One form of rotary kiln in accordance withthe invention will now be described by .way of example with reference tothe accompanying drawings in which:

FIG. 1 is a general elevation of the kiln,

FIG. 2 is an overall longitudinal sectional elevation of the kiln,

FIG. 3 is a longitudinal sectional detail of bearings for the kilnbarrel,

FIG. 4 is an elevation of drive pinion assemblies for the bearings ofFIG. 3,

FIG. 5 is a transverse cross section along the line V- V in FIG. 3,

FIG. 6 is a longitudinal sectional detail of a rotating seal assembly atthe upper end of the kiln barrel in FIG.

FIG. 7 is a longitudinal sectional detail of a rotating seal assembly atthe lower end of the kiln barrel in FIG.

FIG. 8 is a cross section along the line VIII-VlIl in FIG. 2 showingdetails of the inlet hopper at the end of the kiln barrel,

FIG. 9 is a longitudinal sectional detail of one of a member of filterassemblies mounted on the inlet hopper shown in FIGS. 2 and 8,

FIG. 10 is a longitudinal sectional detail of a bearing and sealassembly supporting a scroll member in the DESCRIPTION OF THE PREFERREDEMBODIMENTS I As shown in the general arrangement of FIG. 1 thecomponents of the kiln are supported on structural steelwork comprisinga base assembly 1 carrying a framework 2. The framework 2 comprises twolongitudinal girders 3 joined by cross girders 4. The framework 2 slopesdownwards from one end to the other and is pivoted near its upper end onvertical legs 5 of the base assembly 1. The framework 2 is supportednear its lower end by vertical legs 6 of the base assembly 1. The lowerend of the framework 2 is adjustable in height on the legs 6 of the baseassembly 1 so that the angle of inclination of the framework 2 can beadjusted. lacking means 7 are provided for mechanical raising andlowering of the lower end of the framework Referring also to FIG. 2 thekiln has a cylindrical barrel 8 which is rotatably supported on theframework 2 by bearings 9 at each end of the barrel 8. Each bearing 9has a fixed housing 10 which is mounted on the Iongitudinal girders 3 ofthe framework 2. An inlet hopper 11 is mounted at the upper end of theframework 2. The hopper 11 is additionally supported by springsuspensions 12 from an elevated girder framework 13. The hopper 11 isconnected with the adjacent upper end of the kiln barrel 8 by a rotatingseal assembly 14.

An inlet jet 15 for reactants is provided at the base of the hopper 11which is also fitted with four outlet filter assemblies 16.

A discharge hopper 17 is mounted at the lower end of the framework 2.The discharge hopper 17 is connected with the adjacent lower end of thekiln barrel 8 by a rotating seal assembly 18. A reactant inlet jet 19 isprovided passing through the back face of the discharge hopper 17, intothe kiln barrel 8. The discharge hopper 17 has an outlet pipe 20extending downwards to a product discharge station 21 below the floorlevel of the kiln. The outlet pipe 20 of the discharge hopper 17 has asolids discharge valve 22 at its lower end.

The kiln barrel 8 is fitted with three individual heater units 23 whichare mounted on the longitudinal girders 3 of the framework 2 and whichcan be independently controlled to provide a required temperatureprofile in the kiln barrel 8. The kiln barrel 8 is rotated by a driveunit 24 comprising an electric motor and reduction gear box. The driveunit 24 is suspended from the framework 2 below the bearing 9 at theupper end of the kiln barrel 8. A similar emergency drive unit 25 issuspended from the framework 2 below the bearing 9 at the lower end ofthe kiln barrel 8.

FIGS. 3, 4 and 5 show details of the kiln barrel 8 and the bearings 9.The housing 10 of each of the bearings 9 is cylindrical and is welded toan annular end plate 26. Side mounting brackets 27 are welded to thehousing 10 and the end plate 26 has side extensions 28 formingstiffening webs for the brackets 27. The housings 10 of the bearings 9are supported from the longitudinal girders 3 of the framework 2 by theside mounting brackets 27.

As shown in FIG. 5 a longitudinally grooved bed plate 29 is fitted alongthe upper web 30 of each girder 3 of the framework 2. The bed plates 29run the full length of the girders 3 and are attached to the girders 3by bolts (not shown). Each bed plate 29 has two parallel V-Sectiongrooves 32 along the length of its upper face. A bearing pad 33 isfitted to each of the mounting brackets 27 of the bearing housings 10 bybolts 34. The

under faces of the bearing pads 33 have parallel V-section grooves 35corresponding to the V-section grooves 32 of the bed plates 29.

In the case of the left hand bearing 9 in FIG. 3, that is the bearing 9at the upper end'of the kiln barrel 8, the grooves 35 in the bearingpads 33 of the bearing housing 10 seat on cylindrical rods 36 which liein the grooves 31 of the bed plates 29. The bearing housing 10 isrigidly fixed, at its mounting brackets 27, to the bed plates 29 byshouldered retaining bolts 37.

In the case of the right hand bearing 9 in FIG. 3, that is the bearing 9at the lower end of the kiln barrel 8, the grooves 35 in the bearingpads 33 of the bearing housing 10 seat on ball bearings 38 which asshown in FIG. 5 lie in the grooves 31 of the bed plates 29 below thebearing pads 33. There are eight ball bearings 38 underlying eachbearing pad 33, four in each of the two grooves 35 in the bearing pad33. The eight ball bearings 38 associated with each bearing pad 33 areheld in a ball retaining cage 39 comprising a flat plate with holes inwhich the ball bearings 38 are a clearance fit. The bearing housing 10is held at its mounting brackets 27, on the bed plates 29 by shoulderedbolts 40 such that the bearing housing 10 can move longitudinally to alimited extent on the bed plates 29. The bolts 40 have plain shanks 41which extend through corresponding longitudinal slots 42 in the mountingbrackets 27 of the bearing housing 10 and the bearing pads 33. Theshanks 41 of the bolts 40 are a sliding fit in the slots 42 so that thebearing housing 10 is free to move longitudinally on the bed plates 29to an extent determined by the length of the slots 42.

As shown in FIG. 3 each of the bearings 9 has an annular end plate 44fixed by bolts 45 to the end face 46 of the bearing housing 10. Theouter race 47 of a ball bearing 48 is fitted inside the bearing housing10 between the end plates 26 and 44. The inner race 49 of the bearing 48is fitted on an inner bearing support sleeve 50. The inner bearingsupport sleeve 50 has an external end flange 51 and a gear wheel 52fitted by bolts 53 to the other end 54 of the bearing support sleeve 50.The gear wheel 52 has a center boss 55 which fits over the end 54 of thebearing support sleeve 50. The inner race 49 of the bearing 48 islocated on the bearing support sleeve 50 between the end flange 51 andthe boss 55 of the gear wheel 50.

The kiln barrel 8 has an external flange 56 at each end by means ofwhich the kiln barrel 8 is attached to the gear wheels 52 of thebearings 9 by bolts 57. A linear sleeve 58 of the same diameter as thekiln barrel 8 is welded inside the inner bearing support sleeve 50 ofeach bearing 9.

The ends of the kiln barrel 8 are sealed with the adjoining ends of theliner sleeves 58 by aluminum sealing rings 59 which fit in V-grooves 60in the ends of the liner sleeves 58.

Felt sealing rings 61 and 62 are fitted in grooves 63 respectivelyaround the inner edges of the annular end plates 26 and 44 of thebearing housings 10. The felt sealing ring 61 fits around the end flange51 of the inner support sleeve 50 of the bearings 9 and the felt sealingring 62 fits around the boss 55 of the gear wheel 52 in the bearing 9.

Drive pinions 66 for the bearings 9 are mounted on the side face of theright hand longitudinal girder 3 of the framework 2 as shown in FIG. 5.Referring to FIG. 4 each drive pinion 66 is fitted with a V-grooveddrive pulley 67 on a shaft 68 which is supported in pillow bearingblocks 69 mounted on a base plate 70. The bearing blocks are fixed onthe base plate 70 by bolts 71 and the base plate 70 is fixed to the sideface of the girder 3 by bolts 72 such that the pinion 66 engages withthe gear wheel 52 of the corresponding bearing 9.

As shown in-FIG. 1 the drive unit 24 and the emergency drive unit 25each have a drive shaft 73 fitted with a V-grooved drive pulley 74. Vdrive belts 75 are fitted between the pulleys 67 of the pinions 66 andthe drive pulleys 74 of the drive units 24 and 25.

Referring to FIG. 6 this shows the rotating seal assembly 14 whichconnects the inlet hopper 11 with the adjacent upper end of the kilnbarrel 8.

The rotating seal assembly 14 comprises a central cylinder 76 having awelded external end flange 77. The cylinder 76 is bolted at the endflange 77 to the end flange 51 of the bearing support sleeve 50 in theadjacent bearing 9. An aluminum sealing ring 78 is fitted in a V-groove79 around the inner edge of the end flange 77 on the cylinder 76. Thesealing ring 78 is trapped in the V-groove 79 by a raised annular land80 on the flange 51 of the bearing support sleeve 50.

An inner cylindrical sleeve 81 is mounted in register with a circularopening 82 in the end of the inlet hopper 11. The sleeve 81 has anexternal end flange 83 at which the sleeve 81 is attached by bolts 84 toan annular mounting plate 85 around the opening 82 in the end of theinlet hopper 11. An annular groove 86in the face of the mounting plate85 contains an aluminum sealing ring 87 which is trapped in the groove86 by a raised annular land 88 on the face of the end flange 83 of thesleeve 81. The inner sleeve 81 which extends coaxially inside thecylinder 76 is of smaller diameter than the cylinder 76 so that anannular interspace 89 is defined between the cylinder 76 and the innersleeve 81. An internal flange 90 welded in the end of the cylinder 76extends to the inner sleeve 81 and closes the end of the interspace 89between the cylinder 76 and the inner sleeve 81.

An outer sleeve 91 is mounted coaxially around the cylinder 76. Theouter sleeve 91 has an external end flange 92 at which the outer sleeve91 bolted to the end flange 83 of the inner sleeve 81. An annular groove93 in the face of the end flange 83 of the inner sleeve 81 contains analuminum sealing ring 94 which is trapped in the groove 93 by the endface of the outer sleeve 91. The outer sleeve 91 is of larger diameterthan the diameter of the cylinder 76 so that an annular interspace 95 isdefined between the outer sleeve 91 and the cylinder 76.

An outer seal housing 96 is contained in the interspace between theouter sleeve 91 and the cylinder 76. The seal housing 96 comprises acylindrical body member 97 of slightly smaller diameter than theinternal diameter of the outer sleeve 91. The body member 97 has anexternal end flange 98. An annular seal retaining plate 99 is attachedby bolts 100 to an external end flange 101 on the outer sleeve 91. Anannular groove 102 in the face of the seal retaining plate 99 houses theexternal end flange 98 of the body member 97. An annular groove 103 inthe face of the end flange 101 on the outer sleeve 91 contains a rubberO ring 104. The O ring 104 is trapped in the groove 103 by the externalend flange 98 of the body member 97. Two lip seals 105 separated by alantern ring 106 are fitted in the body member 97 of the seal housing 96between the seal retaining plate 99 and an annular end plate 107 weldedto the inner end face of the body member 97. The ring seals 105 bear onthe outer surface of the central cylinder 76. A channel member 108comprising a cylindric ring 109 having an annular rim 110 is welded tothe face of the annular end plate 107 on the body member 97 of the sealhousing 96. The channel member 108 is fitted with an O ring 111 whichseals with the inner surface of the outer sleeve 91.

An inner seal housing 112 mounted on the end of the central cylinder 76comprises a cylindrical body member 113 which is counterbored to fitover the end of the central cylinder 76. The bodymember 113 is attachedto the end of the cylinder 76 by bolts 114. A lip seal 115 is fittedinside the body member 113 of the inner seal housing 112 between aninternal end flange 116 in the body member 113 and the internal endflange 90 in the end of the central cylinder 76. The ring seal 115 bearson the outer surface of the inner sleeve 81. A nitrogen purge inlet 117is provided in the external end flange 92 of the outer sleeve 91. Afurther nitrogen purge inlet 118 is provided in the wall of the outersleeve 91 in the region of the outer seal housing 96. Drillings 119 inthe body member 97 of the outer seal housing 96 provide for bleeding ofnitrogen into the space between the two ring seals 105.

A helical scroll 120 is welded inside the central cylinder 76 extendingacross the interspace 89 between the central cylinder 76 and the innersleeve 81.

Referring to FIG. 7 this shows the rotating seal assembly 18 whichconnects the lower end of the kiln barrel 8 with the discharge hopper17.

The rotating seal assembly 18 comprises a cylinder 121 having a weldedexternal end flange 122. The cylinder 121 is bolted at the end flange122 to the end flange 51 of the bearing support sleeve 50 in theadjacent bearing 9. An aluminum sealing ring 123 is fitted in a V-groove124 around the inner edge of the end flange 122 on the cylinder 121. Thesealing ring 123 is trapped in the V-groove 124 by a raised annular land125 on the flange 51 of the bearing support sleeve 50. The cylinder 121extends through an aperture 126 in the discharge hopper 17. An outersleeve 127 has an external flange 128 at which the sleeve 127 isattached by bolts 129 to an annular mounting plate 130 around theaperture 126 in the discharge hopper 17. An annular groove 131 in theface of the mounting plate 130 contains an aluminum sealing ring 132which is trapped in the groove 131 by the end face of the outer sleeve127. A lip seal 133 is fitted inside the annular mounting plate 130bearing on the cylinder 121. An annular retaining plate 134 for the ringseal 133 is welded inside the end of the outer sleeve 127.

A seal housing 135 is contained in the interspace between the cylinder121 and the outer sleeve 127. The seal housing 135 comprises acylindrical body member 136 of slightly smaller diameter than theinternal diameter of the outer sleeve 127. The body member 136 has anexternal end flange 137. An annular seal retaining plate 138 is attachedby bolts 139 to an external end flange 140 on the outer sleeve 127. Anannular groove 141 in the face of the seal retaining plate 138 housesthe external end flange 137 of the body member 136. An annular groove142 in the face of the end flange 140 on the outer cylinder 127 containsa rubber O ring 143. The O ring 143 is trapped in the groove 142 by theexternal end flange 137 of the body member 136.

Two lip seals 144 separated by a lantern ring 145 are fitted in the bodymember 136 of the seal housing 135, between the seal retaining plate 138and an annular end plate 146 welded to the inner end face of the bodymember 136. The lip seals 144 bear on the surface of the cylinder 121. Achannel member 137 comprising a cylindrical ring 148 having an annularrim 149 is welded to the face of the annular end plate 146 on the bodymember 136 of the seal housing 135. The channel member 147 is fittedwith an O ring 150 which seals with the inside of the outer sleeve 127.A nitrogen purge inlet 151 is provided in the wall of the outer sleeve127 in the region to the side of the seal housing 135.

As shown in FIGS. 1, 2 and 8 the inlet hopper 11 has an upper section153 and a lower section 154. Referring to FIG. 8 the upper and lowersections 153 and 154 of the hopper 11 have mating flanges 155 and 156 atwhich the sections 153 and 154 are fixed together by bolts 157. Mountingbrackets 158 are welded to the lower section 154 of the hopper 11. Thebrackets 158 support the hopper 11 on the bed plates 29 of the framework2. Similarly to the side mounting flanges 27 of the bearing 9 at thelower end of the kiln body 8, the mounting brackets 158 at the left handend of the solids disentrainment hopper 11 are fitted withlongitudinally grooved bearing pads 33 which seat on ball bearings 38lying in the grooves 31 of the bed plates 29 below the bearing pads 33.The ball bearings 38 below each bearing pad 33 are held in a ballretaining cage 39. The brackets 158 are held on the bed plates 29 byshouldered bolts 40 having plain shanks 41 which extend throughcorresponding longitudinal slots 42 in the brackets 158 and the bearingpads 33 so that the brackets 158 can move longitudinally on the bedplates 29 to a limited extent determined by the length of the slots 42.The brackets 158 at the right hand end of the solids disentrainmenthopper 11 are also fitted with bearing pads 33 but in this case, as inthe case of the bearing 9 at the upper end of the kiln body 8, thebearing pads 33 bear on cylindrical rods which lie in the grooves 31 ofthe bed plates 29 below the bearing pads 33 and the brackets 158 arerigidly bolted to the bed plates 29. I

Further support for the hopper 11, in addition to the support affordedby the spring suspensions 12, is provided by spring loaded tie bars 159which connect with the brackets 158 at the rear end of the hopper 11. Asshown in FIG. 8 the tie bars 159 extend through holes 160 in thebrackets 158. Below the brackets 158 the tie bars 159 are fitted with acoil spring 161 extending between upper and lower spring retainingwashers 162 and 163. The upper spring retaining washer 162 has a domedtop and the lower spring retaining washer 163 is held by retaining nuts164 on the lower threaded end of each tie bar 159. As shown in F 1G. 1the upper ends of the tie bars 159 are connected with the elevatedgirder framework 13.

As shown in FIG. 1 and particularly in H6. 9 the upper section 153 ofthe hopper 11 has a top cover plate 165 which is attached to a topflange 166 of the upper section 153 of the hopper 11 by bolts 167. Thefour outlet filter assemblies 16 of the hopper 11 are mounted inregister with apertures 168 in the topcover plate 165 of the hopper 11.Each filter assembly 16 comprises an annular base plate 169, acylindricalv porous carbon filter element 170, a cover plate 171 for thefilter element and an outer casing 172 enclosing the filter element 170.The filter element 170 seats in an annular groove 173 in the face of thebase plate 169 and is sealed in the groove 173 by jointing compound 174.The upper end face of the filter element 170 seats in an annular groove175 in the underface of the cover plate 171 and is sealed in the groove175 by jointing compound 176. The cover plate 171, which has radialstiffening webs 177, is held by four tie bars 178. The tie bars 178 arescrewed into the annular base plate 169 and extend alongside the filterelement 170.

The upper ends of the tie bars 178 pass through apertures 170 in thecover plate 171 and the end of each tie bar 178 above the cover plate171 is fitted with a coil spring 180 extending between upper and lowerspring retaining washers 181 and 182. The coil springs 180 are held incompression by a nut 183 fitted on the upper threaded end of each tiebar 178. The outer casing 172 of each filter assembly 16 has an endflange 184 at its bottom end. Bolts 185 extending through the end flange184 of the casing 172 and through the annular base plate 169 of eachfilter assembly 16 attach the filter assemblies 16 to the top coverplate 165 of the hopper 11 in register with the apertures 168. Sealingrings 186 are provided between the end flanges 184 of the casings 172and the annular base plates 169 of the filter assemblies 16. Sealingrings 186 are also provided between the annular base plates 168 and thetop cover plate 164 of the hopper 11. The outer casing 172 of eachfilter assembly 16 has a lid 187 which is attached by bolts 188 to aflange 189 at the top end of the casing 172. The casing 172 of eachfilter assembly 16 has an outlet branch pipe 190 near its upper end.

As shown in FIG. 2 the lower section 154 of the inlet hopper 11 containsa longitudinally arranged scroll 191. The lower section 154 of thehopper 11 has a semicircular base 192 conforming to the scroll 191. Thescroll 191 comprises four helical blades 193 welded to supporting rings194. At the rear end of the scroll 191 the blades 193 are welded to anannular end plate 195 by means of which the scroll 191 is supported froma bearing and seal assembly 196 mounted on the rear end wall 197 of thelower section 154 of the hopper 1 1.

The forward end of the scroll 191 extends through the inner sleeve 81 ofthe rotating seal assembly 14 and the liner sleeve 58 of the adjacentbearing 9. A supporting ring 198 is welded to the forward ends of theblades 193 of the scroll 191. Short helical scroll blades 199 are weldedinside the liner sleeve 58 of the bearing 9 co-extensive with the endsof the scroll blades 193. The supporting ring 198 at the ends of thescroll blades 193 fits in a coupling ring 200 welded to the ends of thescroll blades 199 in the liner sleeve 58 of the bearing 9. Catch plates201 are welded to the ends of the scroll blades 199 engaging with theends of the scroll blades 193 of the scroll 191.

An assembly of straight lifting flights 202 is fitted in the kiln barrel8. The lifting flights 202 which are of T cross section are welded tosupporting rings 203. An annular mounting plate 204 is welded to theflights 202 at the lower end of the kiln barrel 8. The mounting plate204 is attached by dowels 205 to an annular end flange 206 in the linersleeve 58 of the bearing 9 at the lower end of the kiln barrel 8. Thesupporting ring 203 for the flights 202 at the upper end of the kilnbarrel 8 is attached by bolts 207 to the kiln barrel 8. Straight liftingflights 208 co-extensive with the flights 202 in the kiln barrel 8 arewelded inside the liner sleeve 58 of the bearing 9 at the lower end ofthe kiln barrel 8 and inside the inner cylinder 121 of the adjacentrotating seal assembly 18.

As shown in FIG. 10 the bearing and seal assembly 196 for the scroll 191is fitted on an annular mounting flange 210 surrounding an opening 211in the rear end wall 212 of the hopper 11. The bearing and seal assembly196 comprises a fixed cylindrical body member 213, a fixed cylindricalbearing support member 214 located coaxially in the body member 213 anda cylindrical bearing housing 215 rotatably mounted on the bearingsupport member 214 inside the body member 218 by a ball bearing assembly216.

The cylindrical body member 213 has an end flange 217 at which the bodymember 213 is fixed to the mounting flange 210 of the hopper 11 by bolts218, an

aluminum joint ring 219 being trapped between the corresponding endfaces of the end flange 217 of the body member 213 and the mountingflange 210 of the hopper 11. The cylindrical bearing support member 214is supported from the body member 213 by an end plate 220 whichis fixedto the end of the body member 213 by bolts 221. The bearing supportmember 214 is welded at one end in an annular groove 222 in the face ofthe end plate 220. The end face of the body member 213 has an annulargroove 223 and an aluminum joint ring 224 is trapped in the groove 223by an annular land 225 on the face of the end plate 220. The ballbearing assembly 216 has an outer race 226 which is fitted in acounterbore 227 in the bearing housing 215. An annular locating ring 228is fitted at the inner end of the counterbore 227 in the bearing housing215. The outer race of the bearing assembly 216 is trapped in thecounterbore 227 of the bearing housing 215 between the annular locatingring 228 and an annular locking ring 229 which is fixed to the rear endface of the bearing housing 215 by bolts 230. A felt ring 231 sealsbetween the inner edge of the annular locating ring 228 and the bearingsupport member 214, the felt ring 231 being fitted in an annular groove232 around the inner edge of the annular locating ring 228. Two lipseals 234 separated by a lantern ring 235 are fitted in a counterbore236 in the body member 213. The lip seals 234 seal against the surfaceof the bearing housing 215 and are trapped in the counterbore 236 of thebody member 213 by an annular end plate 237 which is fixed to the-endflange 217 of the body member 213 by bolts 238. The annular end plate237 fits inside the mounting flange 210 of the hopper 11. An annulargroove 239 around the outer edge of the annular end plate 237 houses anO ring 240 which seals with the inner edge of the mounting flange 210 ofthe hopper 11. A felt ring 241 fitted in an annular groove 242 aroundthe inside of the body member 213 seals about the bearing housing 215adjacent the left hand ringseal 234.

Two lip seals 243 separated by a lantern ring 244 are fitted in thebearing housing 215 to the right of the annular locating ring 228. Thelipseals 243 seal against the surface of the bearing support member 214and are trapped between the annular locating ring 228 and the annularend plate of the scroll 191 which is fixed to the bearing housing 215 bybolts 245. A nitrogen purge inlet 246 is provided through the end plate220 and the bearing support member 214 leading to the region between thelip seals 243. A cross drilling 247 in the bearing housing 215 leadsfrom the lantern ring 244 between the lipseals 243 to the region betweenthe lip seals 234. A nitrogen purge outlet 248 in the end flange 217 ofthe body member 213 leads from the lantern ring 235 between the lipseals 234.

As also shown in FIG. 10 the inlet jet 15 for reactant gases comprisestwo coaxial tubes 250 and 251. An adaptor knob 252, having alongitudinal bore 253, is welded to the end of the outer tube 250, thecorresponding end of the inner .tube 251 being welded in connection withthe bore 253. A screwed plug 254 is fitted in the bore 253 at the end ofthe adaptor knob 252. Two groups of circumferentially spaced lugs 255are welded to the inner tube 251 to maintain the inner tube 251coaxially locatedin the outer tube 250.

An inlet branch 256 for feed of reactant gas through the annularinterspaced between the tubes 250 and 251, is welded in connection withan aperture 257 in the outer tube 250. An inlet branch 258 for feed ofanother reactant gas through the inner tube 251 is welded to the adaptorknob 252 in connection with a cross drilling 259 connecting with thebore 253 in the adaptor knob 252.

The outer tube 250 of the jet 15 is fitted through an aperture 260 inthe end plate 220 of the bearing and seal assembly 196. A mountingflange 261 is welded to the outer tube 250 of the jet 15, the flange 261being fixed to the end plate 220 of the bearing and seal assembly 196 bybolts 262.

The outer tube 250 of the jet 15 also passes through a seal 263 in anend plate 264 which is welded closing the inner end of the bearingsupport member 214 in the bearing and seal assembly 196. The seal 263comprises a bush 265 which is welded in an aperture 266 in the end plate264. The bush has an internal circumferential groove 267 which houses anOring 268 sealing about the outer tube 250 of the inlet jet 15. Anitrogen purge inlet 269 .for the seal 263 is provided in the end plate220 of the bearing and seal assembly 196. Sealing between the mountingflange 261 of the jet 15 and the end plate 220 of the bearing and sealassembly 196 is by means of an interposed joint ring 270.

Referring again to FIG. 2 the discharge hopper 17 is of rectangularcross section, the outlet section 20 of the hopper 17 being tapered andhaving an end coupling flange 271 by means of which the outlet section20 of the hopper 17 is connected with the solids discharge valve 22 inthe product discharge station 21 (See FIG. 1).-A lid 272 having anaccess port 273 is attached to a top flange 274 on the hopper 17 bybolts 275. An annular flange 276 is welded around an aperture 277 in theback face of the hopper 17. A cover plate 278 is fixed to the flange 276by bolts 279. The cover plate 278 has a welded flange plate 280. Thereactant inlet jet 19 comprises a tube 281 which passes throughapertures 282 in the flange plate 280 and the cover plate 278 andextends through the rotating seal assembly 18 and the adjacent bearing 9into the lower end of the kiln body 8. The tube 281 has a mountingflange 283 which is fixed by bolts 284 to the flange plate 280 on thecover plate 278. The tube 281 is sealed in passage through the aperture282 in the cover plate 278 by an O ring seal 285. A further reactantinlet jet 286 is fitted through the side wall of the hopper 17.

A thermocouple tube 287 is located passing longitudinally through thekiln barrel 8 from the rear end of the inlet hopper 11 to the dischargehopper 17. The end of the thermocouple tube 287 in the inlet hopper 11is fixed to a bracket 288 which is attached by bolts 289 to the endplate 264 closing the inner end of the bearing support member 214 in thescroll bearing and seal assembly 196. The other end of the thermocoupletube 287 passes out of the rear end face of the discharge hopper 17through a sleeve 290 set in an aperture 291 in the flange plate 280 andthe cover plate 278 of the hopper 17. O ring seals 292 at each end ofthe sleeve 290 seal the thermocouple tube 287 in passage through thesleeve 290. The end of the thermocouple tube 287 extending outside thesleeve 290, is fitted with a coil spring 293 extending between a seating294 in the flange plate 280 and a spring retaining washer 295 fitted onthe outer threaded end of the thermocouple tube 287. The springretaining washer 295 is held by nuts 296 fitted on the threaded end ofthe thermocouple tube 287. The spring 293 holds the thermocouple tube287 under tension which remains under tension to prevent sagging of thethermocouple tube 287 on longitudinal thermal expansion of thecomponents of the kiln on heating up.

As shown in FIG. 1 the discharge hopper 17 is mounted on the bed plates29 of the framework 2 by side mounting brackets 297. Similarly to thebrackets 27 which mount the housing of the bearing 9 atthe upper end ofthe kiln body 8, the mounting brackets 297 of the discharge hopper 17are rigidly fixed to the bed plates 29 of the framework 2. The brackets297 are fitted with bearing pads 33 which bear on cylindrical rods lyingin the grooves 31 of the bed plates 29 and the brackets 297 are rigidlybolted to the bed plates 29.

The heater units 23 fitted to the kiln body 8 are each mounted on thebed plates 29 of the framework 2 by side mounting brackets 298. In thecase of the center and left hand heater units 23 in FIG. 1 the brackets298 are movably mounted on the bed plates 29 by hearing pads 33 and ballbearings in the manner in which the housing 10 of the bearing 9 at thelower end of the kiln body 8 is mounted. In the case of the right handheater unit 23 in FIG. 1 the right hand pair of brackets 298 are movablymounted in a similar manner on the bed plates 29 but the left hand pairof brackets'298 are rigidly bolted to the bed plates 29. v

Reiterating with regard to the mounting of the various components of thekiln on the framework 2 and referring to FIG. 1 the mounting brackets158 at the right hand end of the solids disentrainment hopper 11 arerigidly bolted to the bed plates 29 of the framework 2 and the mountingbrackets 158 at the left hand end of the solids disentrainment hopper 11are longitudinally movable on the bed plates 29. This allowslongitudinal thermal expansion of the hopper 11 to occur during rise ofthe equipment from ambient to operating temperature.

The brackets 27 mounting the housing 10 of the left I hand bearing 9 atthe upper end of the kiln body 8 are rigidly bolted to the bed plates 29of the framework 2,

whereas the brackets 27 mounting the housing 10 of j the right handbearing 9 at the lower end of the kiln body 8 are longitudinally movableon the bed plates 29. This allows for longitudinal thermal expansion ofthe kiln body 8 again during the rise of the equipment from ambient tooperating temperature. Such longitudinal thermal expansion of the kilnbody 8 is accommodated by sliding of the cylinder 121 of the rotatingseal assembly 18 in the lip seals 133, and 144 of the seal assembly 18(See FIG. 7).

In the case of the heater units 23 as the left hand pair of mountingbrackets 298 on the right hand heater unit 23 are rigidly bolted to thebed plates 29 of the framework 2 and the other pairs of mountingbrackets 298 of the heater units 23 are movably mounted on the bedplates 29 this allows for longitudinal thermal expansion of the heaterunits 23 on rise from ambient to operating temperatures.

By way of example the kiln may be used for carrying out an integratedprocess such as that in which uranium hexafluoride (UP is reacted withsteam to produce uranyl fluoride (UO F and the uranyl fluoride producedby this reaction is then further reacted with steam and/or hydrogen toproduce uranium dioxide.

In use of the kiln for carrying out such a process uranium hexafluoridevapor and dry steam are fed together into the inlet hopper 11 throughthe jet 15. The uranium hexafluoride vapor is fed into the jet 15through the inlet branch 258 and passes through the inner tube 251 ofthe jet 15. The dry steam is fed into the jet 15 through the inletbranch 256 and passes through the annular interspace between the tubes250 and 251 of the jet 15. The uranium hexafluoride and dry steamissuing together from the nozzle of the jet l5 react together (at atemperature of -250 C) in the form of a plume which is directed towardsthe upper end of the kiln barrel 8. Thus the uranyl fluoride which isproduced by the reaction is mainly deposited in the upper end of thekiln barrel 8, although some of the uranyl fluoride falls to the bottomof the inlet hopper 11 or is driven back into the inlet hopper 11 bygases emerging from the kiln barrel 8. The uranyl fluoride passes downthe kiln barrel 8 which is rotated by the drive unit 24.

In passing down the barrel 8 of the kiln the uranyl fluoride is reactedat a higher temperature (500-800 C) with a steam/hydrogen mixture toproduce uranium oxide powder. The required temperature is maintained inthe barrel 8 of the kiln by the heater units 23. The use of a series ofheater units 23 enables the establishment of a required temperaturegradient along the length of the kiln barrel 8. Steam is fed into thelower end of the kiln barrel 8 through the inlet jet 19 and hydrogen ispassed through the inlet jet 286 in the discharge hopper 17.

The lifting flights 202 in the kiln barrel 8 tumble the uranyl fluoridepowder and cause it to move in a downwards spiral path in countercurrentflow to the steam/hydrogen mixture passing upwards through the kilnbarrel 8. The lifting and tumbling motion of the uranyl fluoride powderensures efficient solids/gas contacting and rapid and efficientconversion of the uranyl fluoride powder to uranium oxide powder. Thetumbling of the uranyl fluoride powder in passing down the barrel 8 ofthe kiln also achieves the necessary agglomeration and densification ofthe powder so that the finally produced fluoride free uranium oxidepowder is free flowing and thereby capable of being easily handled inconventional powder handling equipment.

The uranium dioxide produced tumbles into the discharge hopper l7 and isdischarged from the hopper 17 at the discharge station 21 intocontainers coupled with the discharge valve 22 at the lower end of theoutlet pipe 20 of the discharge hopper 17. The annular end flange 206 inthe liner sleeve 58 of the bearing 9 at the lower end of the kiln barrel8 which provides for mounting of the assembly of lifting flights 202 inthe kiln barrel 8, also acts as a spill ring controlling the flow ofpowder out of the kiln barrel 8 into the discharge hopper 17.

The scroll 191 in the inlet hopper 11 is driven by rotation of the kilnbarrel 8 and feeds any uranyl fluoride powder which is deposited in thebase of the inlet hopper 11 into the upper end of the kiln barrel 8.Also the reaction gases entering the inlet hopper 11 from the kilnbarrel 8 are extracted through the filter assemblies 16 on the top coverplate 165 of the inlet hopper 11. The reaction gases are extractedthrough the outlet branch pipes 190 of the filter assemblies 16, passingthrough the carbon filter element 170 of the filter assemblies 16 fromthe inside. Any fine uranyl fluoride powder carried over from the kilnbarrel 8 by the emerging reaction gases is deposited on the inside ofthe filter elements 170 of the filter assemblies 16. Blow backfacilities are provided for the filter assemblies 16 for removal ofaccumulated uranyl fluoride powder which when dislodged from the filterelements 170 falls to the bottom of the inlet hopper 11 and is fed backinto the barrel 8 of the kiln by the scroll 191.

Finally, the design of the rotating seal assembly 14 is such that thelip seals 105 are fully protected from damage by ingress of powder fromthe kiln barrel 8. Access of powder to the lip seals 105 from the kilnbarrel 8 is prevented by the third lip seal 115 which is fitted at theend of the interspace 89 between the cylinder 76 and the inner sleeve 81of the rotating seal assembly 14. Nitrogen purging of the seal housing96 through the purge inlet 118 and of the interspace 95 between theouter sleeve 91 and the cylinder 76 through the purge inlet 117 alsoprevents access of powder to the lip seals 105. Any powder infiltratinginto the interspace 89 between the cylinder 76 and the inner sleeve 81is removed away from the lip seal I by the helical scroll which isfitted inside the cylinder 76.

FIG. 11 shows apparatus for the solid to gaseous conversion of uraniumhexafluoride for supply of gaseous uranium hexafluoride to the rotarykiln in carrying out the process for production of uranium dioxide asdescribed above.

Referring to FIG. 11 a vertically orientated tank 1 is shown having aremovable lid 2. Located in the tank 1 is a cylindrical transportcontainer 3 containing solid phase uranium hexafluoride. Location forthe container 3 in the tank 1 is provided by an annular upstand 4 fittedin the base of the tank 1 and by locking bars 5 pivotably attached tothe walls of the tank 1 immediately below the lid 2 and bearing on thetop of the container 3. The top of the container 3 is provided with alifting attachment 6 and a filler/outlet valve 7. The valve 7 isconnected into a line 8 for supply of gaseous phase uranium hexafluorideto the rotary kiln. Located immediately above the container 3 are twoannular pipes 9 and 10, the internal diameters of which allow thecontainer 3 to be loaded into or removed from the tank 1 withoutdifficulty. Both of the annular pipes 9 and 10 have equidistantly spacedapertures in their inner surfaces which allow water supplied in thepipes to be sprayed onto the top of the container 3. The upper annularpipe 9 is connected to a cold water supply line 11 whilst the lowerannular pipe 10 is connected into a hot water supply line 12 whichextends down towards the base of the tank 1 where it connects into asteam ejector 13. A pipe 14 connects the ejector 13 into the bottom ofthe tank 1 A line 15 supplies steam to the ejector 13. The supply ofsteam to the ejector 13 is controlled by means of an air controlledvalve located in the line 15 which is actuated by an air signal from apressure transducer located in the line 8. Thus the steam supply to theejector 13 is controlled by the pressure of gaseous phase uraniumhexafluoride in the line 8. When the valve 7 is in the open position thepressure of gaseous phase uranium hexafluoride in the line 8 will be thesame as in the cylinder 3.

In operation a container 3 containing uranium hexafluoride in the solidphase is loaded into the tank 1 and located in position by means of theupstand 4 and the locking bars 5. The line 8 is then connected to thevalve 7 which is then opened. Steam is supplied by the line 15 to theejector 13 causing it to draw water 16 from the base of the tank 1 viathe pipe 14 and pass it mixed with steam up the line 12 into the annularpipe 10 from which it emerges as a hot water spray which is directedonto the top of the container 3. The water from the hot spray runs downthe outside of the container 3 and collects in the base of the tank 1where it is available for recirculation by the ejector 13. The hot waterspray heats the walls of the container 3 and converts the solid phaseuranium hexafluoride contained therein into the gaseous phase whichpasses out of the cylinder 3 via the valve 7 into the line 8.

The pressure of the gaseous uranium hexafluoride controls the amount ofsteam supplied to the ejector 13 andhence controls the volume of hotwater sprayed on to the top of the container 3 from the annular pipe 10.In this way the heat supply to the container 3 and thus the rate ofconversion of the uranium hexafluoride from the solid to the gaseousphase is automatically controlled. I

The cold water spray from the annular pipe 9 is used to cool down thecontainer 3 when it is required to stop the conversion of uraniumhexafluoride from the solid to the gaseous phase.

We claim:

l. A rotary kiln comprising a cylindrical kiln barrel rotatably mountedon a supporting framework by a bearing member at each end of the kilnbarrel, an inlet hopper mounted on the supporting framework at one endof the kiln barrel, a discharge hopper mounted on the supportingframework at the other end of the kiln barrel, slidable sealing meansconnecting the inlet hopper with the adjacent end of the kiln barrel,slidable sealing means connecting the discharge hopper with the otheradjacent end of the kiln barrel, the inlet hopper being mounted on thesupporting framework by supports adjacent to each end of the inlethopper, the supports at one end of the inlet hopper being rigidly fixedto the supporting framework, the supports at the other end of the inlethopper being movably mounted on the supporting framework so as to allowfor longitudinal thermal expansion of the inlet hopper relative to thesupporting framework on rise of the inlet hopper from ambient tooperating temperature, the bearing member at one end of the kiln barrelbeing mounted on for longitudinal thermal expansion of the kiln barrelrelative to the supporting framework on rise of the kiln barrel fromambient to operating temperature, the

discharge hopper being mounted at least at one point on the supportingframework by supports which are rigidly fixed to the supportingframework, relative longitudinal movements between the kiln barrel andthe inlet and discharge hoppers due to thermal expansion beingaccommodated by the slidable sealing means between the inlet anddischarge hoppers and the ends of the kiln barrel.

2. A rotary kiln as claimed in claim 1 wherein the supporting frameworkis fitted with longitudinally extending bed plates, the supports for theinlet hopper, the outlet hopper and the bearing members for the kilnbarrel comprising support brackets fitted with bearing pads seating onthe bed plates through intermediate support members, said intermediatesupport members, in the case where the support brackets are movablymounted on the supporting framework, comprising rolling bearing memberslying in longitudinal grooves in the bed plates, the bearing pads havingcorresponding longitudinal grooves in their underfaces seating on therolling bearing members, said intermediate support members, in the casewhere the support brackets are rigidly fixed to the supportingframework, comprising rods lying in the longitudinal grooves in the bedplates, the bearing pads of the support brackets having correspondinglongitudinal grooves in their underfaces seating on the rods and meansbeing provided for clamping the support brackets rigidly to the bedplates with the intermediate rods clamped between the bed plates and thebearing pads on the support brackets.

3. A rotary kiln as claimed in claim I wherein said slidable sealingmeans for connecting either the inlet or the discharge hopper with theadjacent end of the kiln barrel comprises a cylindrical member mountedcoaxially from the end of the kiln barrel and extending longitudinallyinto the annular interspace between inner and outer coaxial sleevesmounted around an aperture in the wall of the related hopper, a lip sealassembly being located in the annular interspace between the outersleeve and the cylindrical member and sealing with the outer surface ofthe cylindrical member, a

second lip seal assembly being located closing the annular interspacebetween the cylindrical member and the .inner sleeve at the end of thecylindrical member remote from the kiln barrel.

4. A rotary kiln as claimed in claim 3 wherein a helical scroll memberis fitted in the annular interspace between the cylindrical member andthe inner sleeve on the side of the second lip seal assembly open to thekiln barrel, the scroll member being mounted on the inner surface of thecylindrical member so rotation of the cylindrical member with rotationof the kiln barrel results in the removal of any powdered material whichinfiltrates into the annular interspace. between the cylindrical memberand the inner sleeve. v

5. A rotary kiln as claimed in claim I wherein a scroll assembly isfitted in the base of the inlet hopper to move any powdered materialwhich deposits in the base of the inlet hopper into the kiln barrel,said scroll assembly being mounted from one end at the end of the inlethopper remote from the kiln barrel by a bearing and seal assembly, theother end of the scroll assembly being coupled with the end of the kilnbarrel so that the scroll assembly is rotated with rotation of the kilnbarrel.

6. A rotary kiln as claimed in claim 5 wherein the scroll assembly is ofskeletal form comprising helical scroll blades mounted on a series ofannular support rings.

7. A rotary kiln as claimed in claim 6 wherein the scroll assembly has acylindrical end support ring at its end adjacent the kiln barrel, theend support ring fitting in a cylindrical extension of the kiln barrel,the kiln barrel having catch plates which engage with and drive thescroll assembly on rotation of the kiln barrel.

8. A rotary kiln as claimed in claim 5 wherein the bearing and sealassembly for the scroll assembly comprises a cylindrical bearing housingmounted on the end of the scroll assembly and extending longitudinallyinto the annular interspace between inner and outer coaxial sleevesmounted from the end wall of the inlet hopper, a bearing member beingfitted in the annular interspace between the cylindrical bearing housingof the scroll assembly and the inner of the coaxial sleeves,

a lip seal assembly being located sealing across the an-

1. A rotary kiln comprising a cylindrical kiln barrel rotatably mountedon a supporting framework by a bearing member at each end of the kilnbarrel, an inlet hopper mounted on the supporting framework at one endof the kiln barrel, a discharge hopper mounted on the supportingframework at the other end of the kiln barrel, slidable sealing meansconnecting the inlet hopper with the adjacent end of the kiln barrel,slidable sealing means connecting the discharge hopper with the otheradjacent end of the kiln barrel, the inlet hopper being mounted on thesupporting framework by supports adjacent to each end of the inlethopper, the supports at one end of the inlet hopper being rigidly fixedto the supporting framework, the supports at the other end of the inlethopper being movably mounted on the supporting framework so as to allowfor longitudinal thermal expansion of the inlet hopper relative to thesupporting framework on rise of the inlet hopper from ambient tooperating temperature, the bearing member at one end of the kiln barrelbeing mounted on the supporting framework by supports which are rigidlyfixed to the supporting framework, the bearing member at the other endof the kiln barrel being mounted on the supporting framework by supportswhich are movably mounted on the supporting framework so as to allow forlongitudinal thermal expansion of the kiln barrel relative to thesupporting framework on rise of the kiln barrel from ambient tooperating temperature, the discharge hopper being mounted at least atone point on the supporting framework by supports which are rigidlyfixed to the supporting framework, relative longitudinal movementsbetween the kiln barrel and the inlet and discharge hoppers due tothermal expansion being accommodated by the slidable sealing meansbetween the inlet and discharge hoppers and the ends of the kiln barrel.2. A rotary kiln as claimed in claim 1 wherein the supporting frameworkis fitted with longitudinally extending bed plates, the supports for theinlet hopper, the outlet hopper and the bearing members for the kilnbarrel comprising support brackets fitted with bearing pads seating onthe bed plates through intermediate support members, said intermediatesupport members, in the case where the support brackets are movablymounted on the supporting framework, comprising rolling bearing memberslying in longitudinal grooves in the bed plates, the bearing pads havingcorresponding longitudinal grooves in their underfaces seating on therolling bearing membErs, said intermediate support members, in the casewhere the support brackets are rigidly fixed to the supportingframework, comprising rods lying in the longitudinal grooves in the bedplates, the bearing pads of the support brackets having correspondinglongitudinal grooves in their underfaces seating on the rods and meansbeing provided for clamping the support brackets rigidly to the bedplates with the intermediate rods clamped between the bed plates and thebearing pads on the support brackets.
 3. A rotary kiln as claimed inclaim 1 wherein said slidable sealing means for connecting either theinlet or the discharge hopper with the adjacent end of the kiln barrelcomprises a cylindrical member mounted coaxially from the end of thekiln barrel and extending longitudinally into the annular interspacebetween inner and outer coaxial sleeves mounted around an aperture inthe wall of the related hopper, a lip seal assembly being located in theannular interspace between the outer sleeve and the cylindrical memberand sealing with the outer surface of the cylindrical member, a secondlip seal assembly being located closing the annular interspace betweenthe cylindrical member and the inner sleeve at the end of thecylindrical member remote from the kiln barrel.
 4. A rotary kiln asclaimed in claim 3 wherein a helical scroll member is fitted in theannular interspace between the cylindrical member and the inner sleeveon the side of the second lip seal assembly open to the kiln barrel, thescroll member being mounted on the inner surface of the cylindricalmember so rotation of the cylindrical member with rotation of the kilnbarrel results in the removal of any powdered material which infiltratesinto the annular interspace between the cylindrical member and the innersleeve.
 5. A rotary kiln as claimed in claim 1 wherein a scroll assemblyis fitted in the base of the inlet hopper to move any powdered materialwhich deposits in the base of the inlet hopper into the kiln barrel,said scroll assembly being mounted from one end at the end of the inlethopper remote from the kiln barrel by a bearing and seal assembly, theother end of the scroll assembly being coupled with the end of the kilnbarrel so that the scroll assembly is rotated with rotation of the kilnbarrel.
 6. A rotary kiln as claimed in claim 5 wherein the scrollassembly is of skeletal form comprising helical scroll blades mounted ona series of annular support rings.
 7. A rotary kiln as claimed in claim6 wherein the scroll assembly has a cylindrical end support ring at itsend adjacent the kiln barrel, the end support ring fitting in acylindrical extension of the kiln barrel, the kiln barrel having catchplates which engage with and drive the scroll assembly on rotation ofthe kiln barrel.
 8. A rotary kiln as claimed in claim 5 wherein thebearing and seal assembly for the scroll assembly comprises acylindrical bearing housing mounted on the end of the scroll assemblyand extending longitudinally into the annular interspace between innerand outer coaxial sleeves mounted from the end wall of the inlet hopper,a bearing member being fitted in the annular interspace between thecylindrical bearing housing of the scroll assembly and the inner of thecoaxial sleeves, a lip seal assembly being located sealing across theannular interspace between the outer of the coaxial sleeves and thecylindrical bearing housing of the scroll assembly, a second lip sealassembly being located sealing across the annular interspace between theinterior of the cylindrical bearing housing and the inner of the coaxialsleeves on the side of the bearing member towards the scroll assembly.